Mac Pro won't power up

Question

I'm running a Mac Pro, 2.66 with 2g memory. The only "custom" modification I've made is to add a second hard drive and partition it for Windows using Boot Camp. I did this shortly after I got the machine (a couple months ago) and it has worked fine since.
We had a power outage locally, and my Mac would have been in sleep mode at the time (I was at work). I have the Mac plugged into a UPS (though I'm not 100% certain of the rating, I bought a fairly large one). The power outage was due to a storm, though the UPS has surge protection also.
When I came home, the Mac was in sleep mode, with the front power LED indicator ON. I could not wake it, and the only way to power it off was to hold the power button.
However, once shut down, the computer will no longer power up. It often clicks when I push the power button, and there's a faint sound / electrical hum like it's going to turn on, but no fan / hard drive noise.
I have attempted to reset the SMC per the directions on the support site. When the mac is unplugged, nothing happens when I hit the SMC_RST button. When it's plugged in, two led indicators flash red.
I've attempted to start it up plugged into the UPS as well as bypassing the UPS and plugging directly into the wall.
I think repair / shot power supply might be my final answer here, but I want to check to see if anyone has any advice before I drive a couple hours to my closest apple store.
Thanks for any assistance, even if it's just, "hey, you're SOL."

Answer 1

I have tried both methods of resetting the SMC (all cables out, plug in, power up, and the second method of opening the thing up and hitting the SMC_RST button, which I've done both plugged in and not) and that doesn't appear to be working.
When I hit the power button, it's obviously getting some juice (lights flicker), there's a click and a faint electric whine, but neither the fans nor the drives start up.
The only other oddity is that two of the LEDs flash red when I hit the SMC_RST button, but they're not on or flashing at any other time.
What confuses me about the issue is that the front power LED was on when I first got home, so it wouldn't seem like it could be a total absence of power (and indeed the flickering of LEDs upon pressing SMC_RST seems to indicate that there's electricity somewhere, at least). However, I can't get fans or drives or even the front LED to light.
I've moved the computer off the UPS and to a different circuit, repeated all SMC_RST steps there, and no luck.
Is there anything that prevents even the fans and drives from starting? (Like, if I don't plug in the keyboard or display, should it at least power up and beep? I've tried with these things plugged in and not plugged in and it doesn't seem to make a difference...)
Thanks